Preparation of oxamide



Get. 25, 1966 E. H. BROWN ETAL 3,281,346

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1966 E. H. BROWN ETAL 3,

PREPARATION OF OXAMIDE 2 Sheets-Sheet 2 Filed June 28. 1965 I E w 4 4 0 0 DR 2M2 ACH H E N L E E L 1 55 EUUN OOI. DDS OH.

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m4 \mmDOI .rFdBOJi W a W United States Patent ()fiice 3,281,346 Patented Oct. 25, 1966 rnnrAnArroN or ()XAMIDE Our invention relates to new and useful improvements in processes for the preparation of oxamide, and more particularly to a process for the preparation of oxamide by the glow-discharge electrolysis of materials selected from the group comprising formamide and alkali cyanides.

Oxamide is a useful, well-known organic chemical intermediate employed in the preparation of other organic compounds and has a substantial potential use as a fertilizer material. Oxamide has a high nitrogen content and a low water solubility which provides a source of nitrogen for the soil which is utilizable slowly over an extended period of time. However, this material has not gained commercial use in the past as a fertilizer due to its relatively high cost.

Heretofore it has been the practice in the chemical industry to produce oxamide by a number of processes including the pyrolysis of ammonium oxalate, treatment of ethyloxalate with ammonia, and by the hydrolysis of cyanogen by concentrated hydrochloric acid.

While previous proposals have been made for the manufacture of oxamide from cyanogen, they have not been carried out commercially because of the initial expense of the cyanogen and the inefficiency of the process of hydrolysis of cyanogen to oxamide. The hydrolysis of cyanogen to oxamide has been previously reported in the literature. In 1860 Von Liebig reported that cyanogen could be treated with an aldehyde to produce oxamide. In U.S. Letters Patent 1,194,354, Bucher, there is disclosed an improved process for hydrolysis of cyanogen to oxamide using concentrated hydrochloric acid. In these teachings it is shown (1) that it is necessary to keep the hydrolysis reaction relatively cool since higher temperatures favor the formation of oxalic acid and (2) that carrying out the hydrolysis of cyanogen under higher pressure increases the formation of oxamide considerably probably due to the increased solubility of cyanogen at higher pressures. In U.S. Letters Patent 2,646,448, Beckham et al., there is disclosed a process for the preparation of oxamide by the pyrolysis of ammonium oxalate in higher yields than have been obtained in the prior art. Beckham et al. discloses the preparation of oxamide by mixing ammonium oxalate and an acidic phosphorus containing catalyst, and heating in a suitable vessel to the temperatures between about 155 C. and about 220 C. for the length of time required for obtaining an optimum yield of oxamide. Beckham shows that in his process wherein no catalyst is utilized the percent of theoretical yield is 28.6 percent as he discloses in his discussion of the prior art and that by means of utilization of various catalysts described in his teachings this percent of theoretical yield may be increased to as much as above 70 percent.

Our invention is directed to a method of producing oxamide by the glow-discharge electrolysis of material selected from the group comprising formamide and alkaline cyanides.

We have overcome the difiiculties inherent in the process of the type of the prior art to a substantial extent in the present invention by a process in one form thereof wherein an acid solution of formamide is subjected to a glow-discharge electrolysis in an electrolytic cell. In our process, a singleor double-compartment electrolytic cell may be used, with the double-compartment cell being preferable because it permits withdrawal of pure hydrogen as .a byproduct. In still another form of our process for the preparation of oxamide, a solution of alkaline cyanide, such as sodium cyanide, is subjected to glowdischarge electrolysis again in a single or double-compartment electrolytic cell. Furthermore, several new and advantageous features over the conventional processes for the production of oxamide shown in the prior art are realized by the preesnt invention.

Among these advantageous features are: a process for the direct production of oxamide wherein the yield, based on chemical equivalents of oxamide produced per Faraday of electricity consumed reaches an efiiciency of 300 percent, which process is characterized by its simplicity, low cost, and short time for carrying out the reaction, and which process is further characterized by the fact that the product therefrom is a pure crystalline product with no substantial amounts of admixed byproducts contained therein, and further, which product requires no purification or upgrading after it is removed or after recovery from the electrolytic cell.

It is therefore an object of the present invention to provide a process for the economical and direct production of oxamide in a state of high purity by the glowdischarge electrolysis of materials selected from the group comprising formamide and solutions of alkaline cyanides.

Another object of the present invention is to provide a process for the economical and direct production of oxamide in a state of high purity, by the glowdischarge electrolysis of materials selected from the group comprising formamide and solutions of alkaline cyanides which process does not require the presence and utilization of catalysts as shown in the prior art.

Still further and more general objects and advantages of the present invention will appear from the more detailed description set forth below, it being understood, however, that this more detailed description is given by way of illustration and explanation only and not by way of limitation since various changes therein may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Our invention will be better understood from a consideration of the following description taken in connection with the accompanying drawing in which:

FIGURE 1 is a side view of the single-compartment cell utilized in our process.

FIGURE 2 is a front view of the double-compartment cell utilized in our process.

FIGURE 3 is a graphical illustration of the effects of temperature on the kilowatt hour requirements per pound of oxamide produced, and more particularly illustrates the preferred operating temperature range wherein the energy requirements are minimized.

The apparatus required in carrying out our process is essentially an electrolytic cell with the cathode in the liquid phase and the anode suspended in the gas phase a short distance above the liquid. In a number of tests employing the electrolytic cell, power for the glow-discharge electrolysis was provided by a 750-Watt rectifier at a maximum potential of 1500 volts.

Referring now more particularly to FIGURES 1 and 2, the cell shown in FIGURE 2 differs from that shown in FIGURE 1 in that the cathode and anode are in separate chambers connected by a permeable membrane illustrated in the drawing as a porous plug. We have found that this design permitted wide variation in the choice of medium used therein and prevented mixing of the gases liberated at the electrodes.

Although we were able to convert pure formamide to oxamide with an electrical efficiency of about percent by our process we found that the efliciency of the conversion was improved severalfold by diluting the formamide with water and by adding an inert electrolyte. In fact, the efficiency was found to be further enhanced by the addition of oxygen to the gas phase surrounding the anode. Among other factors which we were able to determine as having an influencing character on the yield of the oxamide included the concentration of the substrate ('formamide), temperature, and pressure of gas phase. The effect of temperature is graphically illustrated in FIGURE 3.

In order that those skilled in the art may better understand how the present invention can be practiced and more fully and definitely understood, the following examples of processes which we have used in the direct production of oxamide with electrical yields upwards of 100 percent are given by way of illustration and not by way of limitation.

EXAMPLE I Glow-discharge electrolysis of 100 percent formamz'de in cell 1 (a) Thirty ml. of formamide was subjected to 50 ma. at 505 volts for 5.5 hours. The reaction vessel was im- EXAMPLE II Glow-discharge electrolysis 0 formamide-waler mixtures in cell 1 In this series of tests charges of solution ml.) were treated for a period of 5 hours at a power input of 60 ma. and all that was required for smooth operation was, in most cases, approximately 500 volts. The pressure was maintained at mm. Hg absolute and the reaction cell was immersed in ice water in all of the runs. The details and results from this series of tests are given below in Table I.

TABLE I.EFFECT OF CONCENTRATION OF FORMAMIDE AND SUPPLE- MENTAL TREATMENTS Formamide in Yield of Oxamide Run Formamide- Volts Supplemental No. 11 0 Soln., treatment wt. percent Grams EqJF Kwh./1b.

3. 460 0. 4858 0. 99 128. 9 1 gram NH4NO 7. 04 460 0. 9792 1. 99 63. 9 D0. 13. 94 460 1. 2007 2. 44 52. 1 D0. 27. 43 460 1. 2181 2. 47 51. 4 D0. 53. 14 460 0. 9833 2. 00 63. 0 Do. 13. 94 480 1. 0834 2. 20 60. 3 None 27. 43 460 1. 1075 2. 25 56. 5 NH; 27. 43 160 1. 2863 2. 61 48. 7 1 gora rn NIIiNOt,

2 27. 43 505 1. 3560 2. 50. 7 02 27. 43 460 1. 0653 2. 16 58. 8 1 gram NHiCl a Ammonia bubbled through the solution. b Oxygen admitted to upper part of cell. 6 Equivalents per Faraday.

EXAMPLE III Glow-discharge electrolysis of formamide in double-compartment cell A number of tests were run to determine the efiect of addition of an electrolyte to the formamide and the details and results thereof are shown below in Table II.

TABLE II.EFFECT OF ELECTROLYTES OF THE PRODUCTION OF OXAMIDE BY GLOW- DISCHARGE ELECTROLYSIS OF FORMAMIDE [1 hr. runs, 02 admitted to anode compartment, 50 mm. Hg pressure] Charge Yield of Oxamide Amps. Volts Anolyte Catholyte Grams Eq./F Kwh./1b.

10 m1. formamide, 10 ml. Iormamide, 020 600 0.0631 1. 92 86. 3

30 ml. water. 30 ml. water. 10 ml. formamide, 40 ml. water, 1 g. 060 505 0. 2678 2. 72 51.3

30 ml. water, 1 g. NH4NO N H4NO3. 10 ml. lormamide, 40 ml. .8 N H2804..-" 060 460 0.2821 2. 86 44. 4

30 ml. .8 N H2804. 10 ml. Iormamide, 40 ml. butler sol"-.. 060 505 0.2506 2. 54 54. 8

30 ml. buffer sol. 10 ml. lormarnide, 40 m1. .8 N H3PO4 060 500 0. 2798 2. 84 48. 6 30 1111 .8 N 113104.

a Equivalents per Faraday.

EXAMPLE IV EXAMPLE VI In this series of tests the effect of concentration of elec- In the example cited above and shown in Tables I trolyte on the yield of the oxamide was investigated. The through IV, the electrolytic cell was immersed in an iceresults and details of this series of tests are shown below water bath. In this series of tests, the temperature of the in Table III. 5 cooling bath was varied in order to vary the temperature TABLE III.EFFECT OF CONCENTRATION OF ELECTROLYTE ON YIELD OF OXAMIDE BY GLOW-DISCHARGE ELEOTROLYSIS OF FORMAMIDE [1 hr. runs in presence of 0 at 30 mm. Hg pressure] Charge Yield of Oxarnide Amps. Volts Anolyte Catholyte Grams Esp/F Kwh./lb.

fmmamide--m }40 ml. 2 N mso. .060 500 0. 2494 2. 53 54. a

}40 ml. .8 N HgSO 060 460 0. 2914 2. 96 43. 0 10 ml. formamide $8 i N z d }40 ml. .4 N H1804--. 060 443 0. 2875 2. 92 41. 9

In orrnaml e 30 ml l N HZSOL "n }40 m1. .1 N H2804... 660 460 0. 2854 2. 90 43. 9

a Equivalents per Faraday.

EXAMPLE V of the reaction medium and the results therefrom which are tabulated below in Table V indicate that apparently the temperature of the reaction medium has a decided effect on the yield. This effect of the temperature on the yield may, however, be masked by a side effect, namely, a considerable loss of anolyte at the higher temperatures.

In this series of tests the nature of the gas phase ad- 45 mitted to the anode compartment was investigated and the results therein indicated that apparently the nature of the gas phase material has some effect on the yield as is shown below in Table IV.

TABLE IV.EFFECT OF KIND OF GAS IN CATHODE COMPARTMENT ON CI)I%IIIEAM%)DOXAMIDE BY GLOW-DISCHARGE ELEO'IROLYSIS OF [1 hr. runs in presence of 02 at 30 mm. Hg pressure] 1 on at 30 mm. Hg 060 505 0. 2985 3. 03 46. 0 2 CO at 30 nun. Hg 060 505 0. 2672 2. 71 51. 4 3 Air at 30 mm. Hg 060 505 0. 3023 3. O7 45. 5 4 Air at mm. Hg 060 505 0 2927 2. 97 47. O 5 02 at 20 mm. Hg. 060 505 0 2963 3. 01 46. 4 6 N; at mm Hg 060 460 0 2818 2. 86 44. 4 7 N0 gas 060 460 0 2578 2. 62 48. 6

a In each of these tests the charge was'as follows: The anolyte contained 10 m1. formamide and 30 ml. of water, and the catholyte comprised ml. .8 N HZSO4.

Equivalents per Faraday.

TABLE V.-EFFECT OF TEMPERATURE ON THE YIELD OF OXAMIDF. BY GLOW-DISCHARGE ELECTROLYSIS OF F RMAMIDE [0; fed to anode compartment: pressure, 80 mm. Hg abs. current, 0.06

amp. One hour runs] Yield of Oxarnide Anolyte Volts temp.

C. Grams EqJF Kwh./lb.

Double-compartment cell (Fig. 2) Anolyte: 10 ml. formamide and 30 ml. 0.8 N

H230 Catholyte: 40 ml. 0.8 N H 804 Double-compartment cell (Fig. 2) Mixture of 20 m1. iormamide, 60 m1. H 0, and 10 grams N H4NO divided between anolyte and catholyte Single-compartment cell (Fig. 1) 10 ml. formarnide and 30 ml. 0.8 N H1804 n Equivalents per Faraday.

The results shown in Table V above are illustrated graphically in FIGURE 3. We have determined that the preferable operating temperatures at which the operation appears to be most efficient is evidently between about C. and 25 C.

EXAMPLE VII In this series of tests, using the double-compartment cell shown in FIGURE 2, the box design of statistical treatment was utilized to investigate the effects of the five variables: NaCN concentration, NaOH concentration, rate of addition of HCN, pressure, and operating time. The results of this series of tests on glow-discharge electrolysis of cyanide solution is shown in Table VI below.

While We have shown and described particular embodiments in our invention, modifications and variations thereof will occur to those skilled in the art. We wish it to be understood therefore that the appended claims are intended to cover such modifications and variations that are within the true scope and spirit of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A process of preparing oxamide by electrolysis of formamide, which process comprises the steps of introducing liquid formamide into a glow-discharge electrolytic cell, supplying a high-voltage direct current source to said glow-discharge electrolytic cell of voltage sufficient to initiate and maintain a glow-discharge between the anode of said cell and the upper surface of said liquid formamide; subsequently removing from said cell the contents thereof and recovering as a solid product therefrom, by means of filtration, the material oxamide, said process characterized by the fact that the electrical efl'lciency thereof, expressed as equivalents per Faraday, is in the range from about 1 to 3.

2. The process of claim 1 wherein a vacuum is applied to said glow-discharge electrolytic cell and the pressure therein is maintained at less than about mm. of mercury.

3. The process of claim 2 wherein the energy supplied to said glow-discharge electrolytic cell is supplied at approximately 500 volts.

4. The process of claim 3 wherein the material is subjected to the treatment in said glow-discharge electrolytic cell for a period of approximately 3 to 6 hours.

5. The process of claim 4 wherein the temperature of the liquid constituent within said glow-discharge electrolytic cell is maintained in the range from about 0 C. to about 25 C.

6. The process of claim 5 wherein said glow-discharge electrolytic cell is of the double-compartment type such that the compartment housing the anode is separated from the compartment housing the cathode by means of a porous membrane.

7. A process of preparing oxamide, which process comprises the steps of introducing an aqueous alkaline solution of an alkali metal cyanide into a glow-discharge electrolytic cell; supplying a high-voltage direct current source to said glow-discharge electrolytic cell of voltage sufficient to initiate and maintain a glow-discharge between the anode of said cell and the upper surface of said solution; removing from said cell the contents thereof and recovering as a solid product therefrom, by means 50 of filtration, the material oxamide, said process characterized by the fact that the electrical efficiency thereof,

TABLE VL-PREIARATION OF OXAMIDE BY GLOW-DISCHARGE ELEGTROLYSIS OF CYANIDE SOLUTIONS [Power input, ma. at 450 Volts] Operating conditions Power con- Run No. G./100 ml. Time, Oxarnide sumed, kwh./ Eq./F a

Solution HON Pressure, hr. made, grams lb. oxarnide added, mm. Hg

g./l1r. NaOH NaCN Equivalents per Faraday.

expressed as equivalents per Faraday, is in the range from about 1 to 3.

8. The process of claim 7 wherein a vacuum is applied to said glow-discharge electrolytic cell and the pressure therein is maintained at less than about 50 mm. of mercury.

9. The process of claim 8 wherein the energy supplied to said glow-discharge electrolytic cell is supplied at approximately 560 volts.

10. The process of claim 9 wherein the material is subjected to the treatment in said glow-discharge electrolytic cell for a period of approximately 3 to 6 hours.

11. The process of claim 10 wherein the temperature of the solution within said glow-discharge electrolytic cell is maintained in the range from about 0 C. to about 25 C.

12. The process of claim 11 wherein said glow-dis- References Cited by the Examiner UNITED STATES PATENTS 3,155,629 11/1964 Tobin et al. 204-165 X FOREIGN PATENTS 896,113 5/1962 Great Britain.

JOHN H. MACK, Primary Examiner.

H. M. FLOURNOY, Assistant Examiner. 

1. A PROCESS OF PREPARING OXIMIDE BY ELECTROLYTE OF FORMAMIDE, WHICH PROCESS COMPRISES THE STEPS OF INTRODUCING LIQUID FORMAMIDE INTO A GLOW-DISCHARGE ELECTROYTIC CELL, SUPPLYING A HIGH-VOLTAGE DIRECT CURRENT SOURCE TO SAID GLOW-DISCHARGE ELECTROLYTIC CELL OF VOLTAGE SUFFICIENT TO INITIATE AND MAINTAIN A GLOW-DISCHARGE BETWEEN THE ANODE OF SAID CELL AND THE UPPER SURFACE OF SAID LIQUID FORMAMIDE; SUBSEQUENTLY REMOVING FROM SAID CELL THE CONTENTS THEREOF AND RECOVERING AS A SOLID PRODUCT THEREFROM, BY MEANS OF FILTRATION, THE MATERIAL OXIMIDE, SAID PROCESS CHARACTERIZED BY THE FACT THAT THE ELECTRICAL EFFICIENCY THEREOF, EXPRESSED AS EQUIVALENTS PER FARADAY, IS IN THE RANGE FROM ABOUT 1 TO
 3. 